The present invention relates to a method and apparatus for determining the phase (i.e. liquid or gas) of a fluid at a certain level of a container, as well as a method and apparatus for transferring a fluid from a source container into a receiving container using such a method and apparatus.
It is often necessary to determine the level of fill in a fluid container, for example during the process of filling the container, in order not to exceed a predetermined maximum fill level, in order to avoid excessive pressure in the container or, when the fluid in the container is used, in order to determine that the fill level of the container has dropped below a minimum predetermined level, i.e., to detect the imminence of the container becoming empty.
For this purpose, the level at which the transition between the liquid and the gaseous phase of the fluid is located can be detected, but currently such detection can only be done visually through the walls of the container when these walls are transparent, which is only feasible for low-volume containers, such as cigarette lighters.
When the walls of the container are opaque, which is the most frequent case, particularly when the container has a large volume, for example, on the order of one or more liters, visual detection is not possible and then usually the container is weighed with its contents. However, this method is relatively inaccurate, while, when filling a pressurized gas cylinder, a certain safety margin must be provided regarding the fill level of the said enclosure as detected by weighing, in order to avoid excessive filling. Furthermore, this method has the disadvantage of requiring the use of weighing means.